The present invention relates to a plasma processing apparatus and, more particularly, to a plasma processing apparatus adapted to accurately etch fine patterns by applying an RF (radio frequency) bias to samples such as semiconductor devices while using a plasma in order to process the samples.
Today, it is becoming important to control reaction products generated during etching in order to process the surfaces of semiconductor devices accurately. A method for controlling reaction products using a plasma and time modulation of a bias is disclosed as a conventional method in JP-A-8-250479.
Generally, in the case of a pulsed plasma using pulse-modulated microwaves, when the microwaves are activated, free electrons isolate or dissociate other atoms and molecules by energy acquired from the microwaves, thus generating a plasma.
However, when the microwaves are deactivated, free electrons are mostly captured by atoms and molecules in a period on the order of microseconds, producing negative ions. This creates the advantage that charge-up is prevented.